What does unknown signature algorithm mean?

Both registration and login are secure functions on Crayola.com. When you begin them, your browser will switch to secure mode so information you provide is encrypted. However, some older browsers have trouble with the latest certificates used by web sites to enable secure connections. When an older browser attempts a secure connection to Crayola.com, the message you describe is displayed. It is recommended that you upgrade to the latest version of your browser to resolve this problem. For more information about this problem and Internet Explorer on Macintosh computers, please refer to the following Microsoft Knowledge Base article. http://support.microsoft.com/default.aspx?scid=kb;en-us;Q303731&id=303731&SD=MSKB.